In a belt conveyor, the function of the roll is to support the rubber belt and the material being transported, allowing for the rolling movement of the belt. These rolls consist of a cylindrical tube (or shell), and rolling bearings, supported by and fixed to the roll's shaft. The shaft is supported by a frame (or brackets) which in turn is supported by the structure of the conveyor. The rolling bearings of a roll are generally retained to its shaft by means of a spring steel retaining ring, mounted on the shaft and against which a front face of the bearing inner ring rests.
Prior art contemplates a sealing system that aims at offering adequate protection against the entry of dust and moisture while retaining the grease or oil that is necessary for the lubrication of the rolling bearing. The useful life of rolling bearings of a belt conveyor, even if they are correctly dimensioned for the load conditions to which they are subjected, will be severely reduced by contamination if the seal does not offer an adequate protection against the entry of dust and moisture.
In previous constructions, the rolling bearing is generally fixed to the cylindrical tube of the roll by means of a bearing housing (generally a steel sleeve or stamped metal) welded to the end of the cylindrical tube. The bearing housing (or end bell) bends inwardly parallel to the shaft, creating a cavity into which the rolling bearing is press fit. This inward protrusion of the center of the end bell also houses, the various parts that compose the sealing system of the roll, generally of the contact or labyrinth type. The sealing systems are meant to keep dust from entering the roll bearing from outside the roll, and grease from escaping to the inside of the roll.
In these known constructions, the rolling bearing is placed inside the housing, and is separated by a distance D, from the adjacent end of the shaft. The shaft is supported on the structure of the conveyor at the end of the shaft. This support method reduces the load bearing capacity of the roll, by increasing the bending moment of the roll, causing angular deflections in the roll at the bearings. Thus, the useful bearing life is reduced.
Another problem with the known designs of the support roll is the risks posed by the possible fatigue failure of the weldment that affixes the bearing housing to the cylindrical shell. Due to the position of the rolling bearing in relation to the location of the weld, the bearing housing is subjected to an alternating bending moment, thus creating a high risk of failure by fatigue. Specifically, the bearing housing is welded to the adjacent end of the cylindrical shell. The roll bearing is supported by the bearing housing at a position separated from the adjacent end of the roll. Therefore the bearing is separated axially along the roll a distance E. The axial distance E allows for the creation of the bending moment about the roll bearing.
In addition to the inconveniences associated with failed roll assemblies there is the associated damage the failed roll causes to the belt. The damage is in the form of cuts and tears in the belt cover that shortens its life.
In designs where the support is a ring-shaped housing, (generally made of steel), securing parts of the roll (such as by welding) make the roll production work time consuming. On the other hand, attempts to simplify the fixation between components were both problematic and economically unfeasible due to the reduced tolerances required when producing the parts of the assembly. This was particularly the case when applying rigid parts for the ring-shaped housing and for the end element in order to axially lock the cylindrical tube to the shaft.